1. Field of the Invention
The present invention relates generally to a vehicle level changing device of a hydropneumatic suspension unit for a wheeled vehicle and particularly to an improvement in the response of a vehicle level changing device of this type.
2. Description of the Prior Art
As is well known in the art, a hydropneumatic suspension unit used in a wheeled vehicle is usually provided with damping and levelling mechanisms. The damping mechanism serves to absorb and damp by, for example, a gas spring relative vertical movements of the body of the vehicle and wheel supporting means thereof caused by irregularities on the road surface on which the vehicle travels to make riding quality of an occupant of the vehicle comfortable. The levelling mechanism serves to maintain the level of the vehicle body at a constant value independently of a load applied to the vehicle body. Some hydropneumatic suspension units are provided with a level selector mechanism for changing the vehicle body level to an optional value.
However, a conventional level selector mechanism has had a drawback that an undesirably long time is required until the vehicle level changing operation is completed. Because of such a drawback, the vehicle body level has been changed to the optional value as the vehicle body is rolled and pitched to impart a feeling of unrest to an occupant of the vehicle.